JP3791229B2 - Impact rotary tool - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an impact rotary tool used for tightening a bolt, a nut, or a screw.
[0002]
[Prior art]
In order to obtain a higher impact impact force in a conventional impact rotary tool, a heavier hammer, a spring with a high spring constant, and a high-output motor are required. Therefore, in order to ensure the impact impact force, a large amount of electric power must be constantly applied, and even when an impact torque is unnecessary, a loss of electric power that maintains rotation occurs. Further, when the impact impact force is increased, there is a problem that the power loss increases.
[0003]
[Problems to be solved by the invention]
The present invention has been made in view of the above points, and an object of the present invention is to provide an impact rotary tool that cuts useless electric power for maintaining the impact rotation and has a high impact impact force. .
[0004]
[Means for Solving the Problems]
In the impact rotary tool according to claim 1 of the present invention, a cam mechanism 21 is provided between a drive shaft 14 driven by the motor 2 and a hammer 18 for hitting the anvil 19 which is the rotation output unit 5. The hammer 18 and the anvil 19 constitute the striking mechanism 4, and in the impact rotary tool that repeatedly impacts the engagement of the hammer 18 and the anvil 19, the hammer 18 is moved to the motor 2 in synchronization with the impact striking of the hammer 18 on the anvil 19. It is characterized by having a control circuit 23 for turning on and off the power supply.
[0005]
Further, in the impact rotary tool according to claim 2 of the present invention, in addition to the configuration of claim 1, the drive shaft 14 and the hammer 18 are connected to each other via a cam mechanism 21 so as to be relatively rotatable and capable of moving forward and backward. The cam mechanism 21 retreats the hammer 18 with respect to the drive shaft 14 with a delay in relative rotation of the hammer 18 with respect to the drive shaft 14, and is compressed by the retraction of the hammer 18 to advance the hammer 18. A hammer spring 17 for accumulating the hammer 18, the hammer 18 is advanced by the spring force accumulated in the hammer spring 17, and the hammer 18 is rotated by the cam mechanism 21 to impactably engage the anvil 19. It is what.
[0006]
The impact rotary tool according to claim 3 of the present invention operates in addition to the configuration of claim 1 or 2 and operates with the battery 36 as a power source, and boosts the battery power supply voltage to supply power to the motor 2. The control circuit 23 sometimes includes a booster circuit 24 that applies a voltage higher than the battery power supply voltage, and the control circuit 23 activates the booster circuit 24 while the hammer 18 strikes the anvil 19 to cause the capacitor 35 to exceed the battery power supply voltage. it is characterized in that the charges of the charge and the hammer 18 at the timing of storing striking force to the motor 2 is intended to supply power from the capacitor 35.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
[0008]
An example of an embodiment of the present invention is shown in FIGS. The impact rotary tool includes a main body 1 and a battery pack 25 that is detachable from the main body 1. The main body 1 includes a main portion 1a and a grip portion 1b. The main part 1 a includes a motor 2, a speed reducer part 3, an impact mechanism part 4, and a rotation output part 5. In addition, the grip portion 1b includes a control circuit 23 and the like, and a power switch 38 is provided.
[0009]
Hereinafter, the structure of the main part 1a of the main body 1 will be described in order from the rear side. The motor 2 is disposed at the rearmost portion of the main portion 1a. In this example, a gap is provided between the rear wall of the main portion 1a and the motor 2, and a switching element 26 described later is disposed inside the rear wall. To do.
[0010]
The reduction gear unit 3 is disposed on the front side of the motor 2, and the reduction gear case 22 is fixed to the front surface of the motor 2 with screws 27. A ring gear 9 is provided on the front inner peripheral wall 22 a of the speed reducer case 22, and the planetary gear mechanism 6 is configured in the speed reducer case 22. That is, the tip of the rotating shaft 2a of the motor 2 is the sun gear 7, and a plurality of planetary gears 8 are arranged around the sun gear 7, and the sun gear 7 and the planetary gear 8, and the planetary gear 8 and the ring gear are arranged. 9 is in a state of being engaged with each other. The center of each of the plurality of planetary gears 8 is fixed by a fixed shaft 10 inserted through the carrier 11. A shaft 13 is continuously formed on the front side of the carrier 11, and becomes an integral part (hereinafter referred to as a drive shaft 14) composed of the shaft 13 and the carrier 11, and is driven as an output shaft of the planetary gear mechanism 6. The drive shaft 14 is held by a bearing 28 whose rear end is held in the speed reducer case 22 and its front end is held by a rear hole 19b of the anvil 19 so that its central axis is The main body 1 is held so as to be coaxial with the central axis of the main portion 1a.
[0011]
The striking mechanism unit 4 will be described. After the spacer 29, the spring receiving plate 15, the hammer spring 17, and the spring receiving plate 16 are sequentially fitted to the drive shaft 14 from the right side in FIG. 1, the drive shaft 14 is inserted into the hole 18b of the hollow convex hammer 18. The hammer spring 17 is inserted between the front end face of the fixed shaft 10 and the rear end face of the hammer 18 via the spring receiving plates 15 and 16, and the hammer 18 is biased with a spring.
[0012]
As shown in FIG. 1, two leads 18c are provided on the front inner circumference of the hammer 18 so as to allow the hemisphere of the steel ball 20 to enter, thereby forming a hammer cam 18d. Correspondingly, two leads 14c are vertically provided on the front outer periphery of the drive shaft 14 so that the hemisphere of the steel ball 20 can enter the V shape (the front is the closed side of the V shape). The shaft cam 14d is formed, and the hammer 18 and the drive shaft 14 are connected via a steel ball 20 in a space formed by overlapping the hammer cam 18d and the drive shaft cam 14d, thereby forming a cam mechanism 21. When the impact rotary tool is not used, the hammer 18 is spring-biased, so that the hammer 18 moves to a position where it can be advanced to the maximum with respect to the drive shaft 14, and the steel ball 20 is driven accordingly. It moves to the tip of a V-shaped drive shaft cam 14d provided on the shaft 14.
[0013]
A plurality of hammer claws 18a are formed radially at the front end of the hammer 18, and the rear part of the anvil 19 which is the rotation output part 5 is hooked so as to face the hammer claw 18a. A plurality of hammer engaging portions 19a are formed radially.
[0014]
At the rear of the anvil 19, there is provided a rear hole 19b through which the front end shaft portion 14a of the drive shaft 14 protruding from the front end surface of the hammer 18 is inserted, and a bit mounting hole for mounting a bit (not shown). 19c is provided from the front end face to the middle of the anvil 19. And the anvil 19 is hold | maintained at the main body 1 via the bearing metal 30, and the axial part 19d protrudes from the front side end surface of the main body 1. FIG.
[0015]
A chuck 31 can be slidably coupled to the outer periphery of the protruding portion of the shaft portion 19d. Then, a hole 19e into which a steel ball 32 for pressing and fixing the bit is fitted is provided on the outer periphery of the protruding portion of the shaft portion 19d. When the bit is mounted, the bit is first inserted into the bit mounting hole 19c, When the chuck 31 is slidably coupled to the outer periphery of the protruding portion of the shaft portion 19d, the convex portion provided on the inner peripheral surface of the chuck 31 pushes the steel ball 32 into the shaft portion 19d, and the steel ball 32 presses the side surface of the bit. Therefore, the bit can be fixed to the shaft portion 19 d of the anvil 19.
[0016]
Next, the operation of this impact rotary tool will be described.
[0017]
The rotation of the motor 2 is decelerated by the reduction gear unit 3 and output to the drive shaft 14. The rotation of the drive shaft 14 is transmitted to the hammer 18 through the steel ball 20. Then, when the hammer claw 18 a formed at the front end portion of the hammer 18 engages with the hammer engaging portion 19 a formed at the rear end portion of the anvil 19, the rotation of the hammer 18 is transmitted to the anvil 19.
[0018]
Here, consider a case where a large load is applied to the anvil 19. At this time, the rotation of the anvil 19 is relatively slow with respect to the hammer 18. Along with this, the rotation speed of the hammer 18 also decreases. Then, since the hammer 18 cannot synchronize with the rotation of the drive shaft 14, the steel ball 20 moves backward in the R direction along the lead 14 c from the V-shaped tip of the drive shaft cam 14 d at the initial position. As a result, the hammer 18 moves backward in the R direction with respect to the drive shaft 14 and compresses the hammer spring 17. When the hammer 18 advances to a position with respect to the drive shaft 14, the hammer claw 18a of the hammer 18 comes off from the hammer engaging portion 19a of the anvil 19, and the hammer claw 18a gets over the hammer engaging portion 19a. At this time, the hammer 18 moves forward in the F direction with respect to the drive shaft 14 as the steel ball 20 advances in the F direction along the V-shaped lead 14c of the drive shaft cam 14d by the restoring force of the hammer spring 17. Then, the hammer claw 18a of the hammer 18 and the hammer engaging portion 19a of the anvil 19 are engaged with each other again so as to give a rotational force to the anvil 19.
[0019]
Incidentally, a proximity sensor 34 is disposed in the main body 1 as a sensor 33 for detecting the axial movement of the hammer 18 on the upper inner wall of the bush portion 18e of the hammer 18. The output signal of the proximity sensor 34 is maximized at the position where the hammer 18 is most retracted (FIG. 2).
[0020]
The motor 2 is wired in series with a switching element 26 such as a MOS-FET and a power source 36 (battery pack 25). The switching element 26 turns on / off the power supply to the motor 2 by the control circuit 23.
[0021]
In a series of impact motions, the motor 2 is initially energized because the switching element 26 is initially in an on state. When a load is applied to the anvil 19, the hammer 18 is retracted in the R direction in response to this, and the hammer spring 17 is compressed. When the hammer 18 moves backward in the R direction and moves back to a position where the engagement between the hammer pawl 18a and the hammer engaging portion 19a is disengaged, the proximity sensor 33 detects this, and the control circuit 23 turns off the switching element 26. And the motor 2 is turned off. From the moment the hammer claw 18a and the hammer engaging portion 19a are disengaged and the hammer claw 18a gets over the hammer engaging portion 19a, the hammer claw 18a is shockedly engaged (struck). The driving force required for the motor 2 until this time may be sufficiently small as compared with the case where the hammer spring 17 is driven in a compressed state. Absent.
[0022]
Further, a separate proximity sensor may be provided to detect the advance of the hammer 18, but the moment when the hammer claw 18a and the hammer engaging portion 19a are disengaged and the hammer claw 18a gets over the hammer engaging portion 19a. Since the time until the hammer claw 18a is shockedly engaged with the hammer engaging portion 19a is substantially determined by the spring constant of the hammer spring 17 and the natural frequency due to the weight of the hammer 18, it is not detected by the sensor. In addition, the energization cut-off time is set to a certain time. The energization cut-off time is set in advance by the control circuit 23. In this case, when the hammer claw 18a is shockedly engaged with the hammer engaging portion 19a, or the energization cut-off time set immediately before the engagement is over, energization is started again, and the impact rotary tool is driven. FIG. 3 shows a circuit diagram of this impact rotary tool.
[0023]
4 and 5 are graphs showing the motor current value, the motor rotation speed, and the torque value generated in the anvil 19 in the time series in operation of the impact rotary tool of this example and the impact rotary tool of the conventional example. As can be seen by comparing the two, in this example, the motor claw between the moment when the hammer claw 18a gets over the hammer engaging portion 19a and the moment when the hammer claw 18a is shockedly engaged with the hammer engaging portion 19a. Since the power is controlled to be cut off, the power during this period can be saved. As a result, the heat generation of the motor 2 can also be suppressed.
[0024]
Another example of the embodiment of the present invention is shown in FIGS. In this example, the mechanical configuration excluding the electric circuit is the same as that in the above example, and the description thereof is omitted. A circuit diagram of the impact rotating tool of this example is shown in FIG. In this circuit, a booster circuit 24 connected to a capacitor 35 is added to the control circuit 23, and a switching element 37 for the booster circuit 24 is provided separately from the switching element 26. The operation of this example will be described. After the hammer claw 18a gets over the hammer engaging portion 19a and before the hammer claw 18a is impactably engaged with the hammer engaging portion 19a, the booster circuit 24 is activated, The capacitor 35 is charged with a charge equal to or higher than the power supply voltage, a load is applied to the hammer 18, the hammer spring 17 is compressed, and the capacitor 35 is stored in the capacitor 35 until the hammer claw 18a and the hammer engaging portion 19a are disengaged. A charge equal to or higher than the power supply voltage is applied to the motor 2. As a result, the driving force for retracting the hammer 18 can be increased, so that the compression force of the hammer spring 17 can be increased.
[0025]
FIG. 7 shows the motor current value and motor voltage during operation of the impact rotary tool (A) having the circuit configuration of FIG. 6 and the impact rotary tool (B) having the circuit configuration of FIG. 5 is a graph comparing the motor rotation speed and the torque value generated in the anvil 19 in time series. As can be seen from FIG. 7, in the impact rotary tool (A) having the circuit configuration of FIG. 6, a high driving force can be obtained by applying a voltage higher than the battery voltage when the hammer spring 17 is compressed. The time required for compression is short, and the impact operation can be speeded up.
[0026]
FIG. 8 shows an impact rotary tool having the same circuit configuration as that of FIG. 6, in which a heavy weight hammer 18 and a high spring constant hammer spring 17 are used (C), and a standard weight hammer 18 and a standard spring constant are obtained. It is the graph which compared the motor current value at the time of operation | movement, a motor voltage, the motor rotation speed, and the torque value which generate | occur | produces in the anvil 19 in time series about the case (D) which uses the hammer spring 17 which has. In this case as well, since a high driving force can be obtained by applying a voltage higher than the battery voltage when the hammer spring 17 is compressed, the hammer spring 17 having a heavy weight and the hammer spring 17 having a high spring constant can be obtained. Can be easily compressed, and by releasing the hammer spring 17, a high impact impact force can be generated on the anvil 19.
[0027]
In addition, if this configuration is used, the same output as the conventional one can be realized by the lightweight hammer 18 and the hammer spring 17 having a low spring constant, so that the size and weight can be reduced.
[0028]
【The invention's effect】
In the invention according to the first aspect of the present invention, since the energization time can be shortened, power can be saved and heat generation of the motor can be suppressed.
[0029]
In the invention according to claim 2 of the present invention, in addition to the effect of the invention according to claim 1, the structure of claim 1 can be realized with a simple structure.
[0030]
In addition, in the invention described in claim 3 of the present invention, in addition to the effect described in claim 1 or 2, the driving force for retracting the hammer can be increased, so that the working time can be shortened. Also, a higher output can be realized by using a heavy hammer and a spring having a higher spring constant than conventional ones. Further, since the same output as the conventional one can be realized by a light hammer and a hammer spring having a low spring constant, it is possible to reduce the size and weight.
[Brief description of the drawings]
FIG. 1 shows an example of an embodiment of the present invention and is a longitudinal sectional view of an impact rotary tool.
FIG. 2 is a longitudinal sectional view of a part of the impact rotary tool.
FIG. 3 is a circuit diagram of the impact rotary tool of the above.
FIG. 4 is a graph showing in time series the motor current value, the motor rotation speed, and the torque value generated in the anvil when the impact rotary tool is operated.
FIG. 5 is a graph showing, in a time series, motor current values, motor rotation speeds, and torque values generated in an anvil during operation of a conventional impact rotary tool.
FIG. 6 is a circuit diagram of an impact rotary tool according to another example of the embodiment of the present invention.
7 shows, in time series, the motor current value, the motor voltage, the motor speed, and the torque value generated in the anvil during operation for the impact rotary tool having the circuit configuration of FIG. 3 and the impact rotary tool having the circuit configuration of FIG. It is the graph compared.
8 shows an impact rotary tool having the circuit configuration shown in FIG. 6; motor current value, motor voltage, motor rotation speed, and torque generated in the anvil when the weight of the hammer and the spring constant of the hammer spring are different. It is the graph which compared the value in time series.
[Explanation of symbols]
2 Motor 4 Blowing mechanism section 5 Rotation output section 14 Drive shaft 17 Hammer spring 18 Hammer 19 Anvil 21 Cam mechanism 23 Control circuit 24 Booster circuit

Claims (3)

  A cam mechanism is provided between the drive shaft driven by the motor and the hammer for anvil that is the rotation output part. The drive mechanism is composed of the drive shaft, the hammer and the anvil, and the hammer and the anvil are engaged. An impact rotary tool characterized by having a control circuit for turning on and off power supply to a motor in synchronization with impact impact of a hammer on an anvil.   The drive shaft and the hammer are connected to each other via a cam mechanism so that they can rotate relative to each other and can move forward and backward. The cam mechanism retracts the hammer with respect to the drive shaft when the hammer rotates relative to the drive shaft. A hammer spring that accumulates a spring force that is compressed by the retraction of the hammer and accumulates the hammer is provided, the hammer is advanced by the spring force accumulated in the hammer spring, and the hammer is rotated by the cam mechanism to anvil the hammer. 2. The impact rotary tool according to claim 1, wherein the impact rotary tool is engaged with the impact rotary tool. It operates with a battery as a power source, and has a booster circuit that boosts the battery power supply voltage and applies a voltage higher than the battery power supply voltage when supplying power to the motor. The control circuit has a hammer that strikes the anvil. characterized in that the motor in accordance with the timing and hammer activates the booster circuit to charge the battery power source voltage or charge on the capacitor is storing a striking force is intended for supplying power from the condenser while The impact rotary tool according to claim 1 or 2.

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